Method for the processing of synthetic fibers used for reinforcing rubber

ABSTRACT

A method for the treatment of synthetic fibers used for reinforcing rubber, featuring treatment of the synthetic fiber used for reinforcing rubber with a treating agent in which a nonionic surface active agent (abbreviated as X below) with the following general formula:   WHERE A represents (CH2)7-CH=CH-CH2 or (CH2)10; R1, R2 and R3 represent hydrogen atoms or -CO-R&#39;&#39;1, -CO-R&#39;&#39;2, and -CO-R&#39;&#39;3; R&#39;&#39;1, R&#39;&#39;2 and R&#39;&#39;3 represent aliphatic hydrocarbons with carbon numbers of 1 to 22; p, q, and r represent the molar numbers of the ethylene oxide added and p + q + r is a positive integer 50 to 300; IS COMBINED WITH PARTIALLY OXIDIZED POLYETHYLENE WITH AN AVERAGE MOLECULAR WEIGHT OF 500 TO 10,000 (Abbreviated as Y below) in proportions within the limits of X 5 to 40, Y 0.1 to 3.0, and in which these components are combined with a lubricating agent and a surface active agent in addition to the aforesaid nonionic surface active agent X to give a total quantity of 100 weight percent.

United States Patent Honda et al.

[151 3,661,629 51 May 9, 1972 [54] METHOD FOR THE PROCESSING OF SYNTHETIC FIBERS USED FOR REINFORCING RUBBER [72] Inventors: Kyomi Honda; Koji Misaki, both of Mihara, Japan [58] Field of Search ..260/484 R; 106/295; 117/138.8 F, 138.8 N, 77,139.5 F

[56] References Cited UNITED STATES PATENTS 9/1963 Ross ..117/161X 6/1968 Crovatt ....260/3l.4X

3,218,222 11/1965 Skeen et a1... ..1l7/l38.8 N

3,282,724 l1/l966 Atwell ..117/138.8 N

3,437,610 4/1969 Moult ..1l7/138.8 N

3,443,986 5/1969 Watanabe et a1. ..1 17/138.8 N

3,525,206 8/1970 Hersh et a1 ..117/138.8 N

FOREIGN PATENTS OR APPLlCATlONS 682,354 3/1964 Canada ..l17/l38.8 N

Primary E.\'aminerWilliam D. Martin Assistant Examiner-Sadie L. Childs Attorney-Richard A. Anderson and Roy H. Massengill 57 ABSTRACT A method for the treatment of synthetic fibers used for reinforcing rubber, featuring treatment of the synthetic fiber used for reinforcing rubber with a treating agent in which a nonionic surface active agent (abbreviated as X below) with the following general formula:

O-(CHz-CHz-Ob-Ih where A represents (Cl-l2)-,CH=Cl-l-CH2 or (CH-2). R1, R2 and R3 represent hydrogen atoms, or CO-R' COR and -C0-R RH, R and R' represent aliphatic hydrocarbons with carbon numbers of l to 22; p, q, and r represent the molar numbers of the ethylene oxide added and p+q+r is a positive integer=5 to 300; is combined with partially oxidized polyethylene with an average molecular weight of 500 to 10,000 (Abbreviated as Y below) in proportions within the limits of X=5 to 40, Y=0.l to 3.0, and in which these components are combined with a lubricating agent and a surface active agent in addition to the aforesaid nonionic surface active agent X to give a total quantity of 100 weight percent.

4 Claims, No Drawings METHOD FOR THE PROCESSING OF SYNTHETIC FIBERS USED FOR REINFORCING RUBBER BACKGROUND OF THE INVENTION The present invention pertains to a method for processing synthetic fibers that are used for reinforcing rubber.

The objectives of this invention are to prevent the reduction in the strength of synthetic fibers used for strengthening rubber during hot bonding treatment, by treating the synthetic fiber used for reinforcing rubber with a special processing agent to improve strength, and in addition, to improve adhe sion, heat resistance and fatigue resistance in such fibers it is the usual practice, when synthetic fibers used for reinforcing rubber are mixed in with the rubber, to treat the compound with bonding agents and to accomplish heat treatment for the purpose of improving the adhesion between the fiber and the rubber.

in such cases, the synthetic fiber used for reinforcing rubber that has been so treated has the defect of a loss in its fatigue resistance.

It is well known that partially oxidized polyethylene has been used for the treatment of polyamide fibers as a means of meeting this problem in Japanese Pat. Not. 1968-16667. The increase in strength that should be expected cannot be produced by applying the treatment only to the cord as in the process covered by that invention. It also has the deficiency of reducing the bonding strength and the fatigue resistance of the cord.

Further, the concurrent utilization in the heat treatment of synthetic fibers of partially oxidized polyethylene and the emulsifiers polyoxyethylene-( 20)-lauryl ether or polyoxyethylene-(20)-lauryl ester is well known in U. S. Pat. No. 3,103,448. These processing agents do not increase the strength of the cord adequately and are undesirable because they also reduce the bonding properties and fatigue resistance of the cord As a result of studies intended to eliminate these defects, the writers arrived at the knowledge, which formed the basis for this invention, that the treatment of synthetic fiber for reinforcing rubber with partially oxidized polyethylene and a special emulsifier in a compound containing both in appropriate proportions would increase the strength of the fiber and would, in addition, increase its bonding with the rubber, heat resistance and resistance to fatigue.

SUMMARY OF THE INVENTION Specifically, the present invention is a method of treating synthetic cord used for reinforcing rubber which has as its special feature the combination of nonionic surface active agent (abbreviated as X below) having the following general formula:

O(CH2CH2O),-R;

in the above formula, A represents (CI-I -CH CH-CI-I, or (Cl-1 m. R,, R R represent hydrogen atoms or -CO-R,, CO-R',, or -CO-R' R,, R and R' represent aliphatic hydrocarbons with carbon numbers of l 22. Further p, q, and r represent the molar numbers of the ethylene oxide added and p q r is a positive integer 5 to 300. with partially oxidized polyethylene (abbreviated as Y below) having an average molecular weight of 500 to 10,000, within the limits, by weight percent, of the X 5 to 40, Y 0.1 to 3.0. This is then treated with a processing agent comprising a lubricating agent and a surface active agent in addition to the aboveidentified nonionic surface active agent, X, to give a total quantity of 100 weight percent.

The form of the synthetic fiber used for reinforcing rubber as covered in the present invention may be (for example) tire cord, belt cord, fibers used in waterproofing or other industrial fibers.

The synthetic fiber used in the present invention, may be, for example, a polyester, or a polyamide, etc.

In the process covered by the present invention, the treating agent covered by the present invention may be added to the fiber during any process from the spinning of the said rubber reinforcing fiber, up to the hot bonding treatment.

The values for p, q and r for the nonionic surface active agent used in the present invention represent the total molar numbers for the ethylene oxide added. It is mandatory that p q r 5 to 300. It is possible to dramatically increase the strength of the rubber treated within these limits. Particularly desirable results can be obtained within the limits of p q r 10 to 150. It is undesirable that the total be less than p q r 5 as this reduces the bonding strength of the treated cord. It is also undesirable that the total be more than p q r= 300 as this makes emulsification difficult and the cord which is treated becomes stiff and loses strength.

In the nonionic surface active agent covered by the present invention, R R and R represent aliphatic hydrocarbons with carbon numbers of 1 to 22. The presence or absence of branched chains or double bonds is irrelevant. No exceptional difference is observed in improving the strengthening effects of the synthetic fiber used for reinforcing rubber within the above described limits for aliphatic hydrocarbons with carbon numbers of more than 22, but emulsifiability is lost and the compound cannot be put to practical use. Carbon numbers of 8 to 17 are desirable in the aliphatic hydrocarbon from the viewpoint of the emulsifiability and the solubility of the processing compound.

it is possible to use only the nonionic surface active agent in the present invention and still increase the strength of the synthetic fiber used for reinforcing rubber. ln such cases, however, it is necessary to increase the proportions of this agent within the treating compound to more than weight percent in order to achieve the desired increase in strength. It is not desirable to do so since this reduces bonding strength. This also has a markedly deleterious effect on the spinnability when it is utilized as a spinning oil in spinning. It can also not be used industrially owing to the extreme difficulties engendered in dissolution or emulsifying when it is used in an aqueous emul- As a result of the utilization of the partially oxidized polyethylene and the nonionic surface active agent in the optimum proportions as covered in the present invention, it has been possible to overcome these obstacles and to increase dramatically the bonding properties and fatigue resistance during the strengthening of the treated cord.

It is mandatory that the partially oxidized wax utilized in the present invention be a partially oxidized polyethylene type wax with an average molecular weight of 500 to 10,100.

It is desirable that the acid value of the partially oxidized wax be 10 to 30, and that the softening point be below 125 C.

The commercial, partially oxidized waxes which fulfill these conditions are the partially oxidized microcrystalline waxes, for example, Petrolite C-5, C-23, C-36, PE and Petronauba C, D, F, H and W, etc. The partially oxidized polyethylene waxes may be, for example, Hexto Wax Pead 521, Hexto Wax V P-522, Ebolene E and AC-655, etc.

It is necessary to add a lubricating agent and a surface active agent in addition to the nonionic surface active agent, X, to the previously described effective components in the processing agent used in the present invention. So long as the composition is maintained within the limits components X and Y, where X 5 to 40 weight percent and Y 0.1 to 3.0 weight percent, the lubricating agent and the surface active agent do not interfere with the cord strengthening efi'ects of the processing agent. The smoothing agent and the surface active agent may be added to component X and Y in quantities that will make the total quantity of the compound 100 percent.

The lubricating agent in the present invention may be mineral oil, a higher aliphatic alcohol ester or a vegetable oil, etc. The active agent which can be used together with these substances may be a nonionic surface active agent, except for the nonionic surface active agent X, for example, an addition compound of a higher alcohol and ethylene. oxide. The ionic type surface active agent that may be used are, for example, a sulfuric acid ester salt, a phosphoric acid ester salt, etc. These lubricating agents and surface active agent improve the emulsifiability,the solubility and the smoothness of the processing agentand facilitate the spinning process and the cord manufacturing process.-

In the process covered by the present invention, the treating agent may be applied to the synthetic fiber used for reinforcing rubber at any time from its spinning up to the heat bonding process by immersion, spraying, or any other suitable method for applying a thin coating to the fiber. The treating agent may be applied to the fiber as is, but it may also be used in a form of an aqueous emulsion or be dissolved in a solvent.

Fully adequate efiects may be attained by applying the treating agent in quantities of 0.01 to 2.00 weight percent to the fiber being treated.

1n the present invention, as a result of treating synthetic fiber used for reinforcing rubber with a treating agent composed of the special nonionic surface active agent X, and partially oxidized polyethylene Y, in quantities that lie within the limits X to 40 weight percent, Y 0.1 to 3.0 weight percent, and a mineral oil and a surface (except for the above stated X), in quantities that will give a total weight percent of I00, in small quantities, make it possible to greatly increase the cord strength, its adhesion and its resistance to fatigue subsequent to bonding heat treatment. it is possible to improve spinnability by utilizing the treating agent covered by the present invention by using it as a spinning oil or a stretching oil during spinning and stretching.

The treatment covered by the present invention is particularly advantageous when used with polyamide fibers or polyester fibers that are used in tire cord.

DESCRIPTION OF THE PREFERRED EMBODIMENTS degreased. This cord was then immersed in a2 percent aqueous emulsion of a treating agent having the various compositions shown in Table l as tests [-15 and the blank test. After applying 0.5 weight percent of the treating agent to the cord, 8 percent of the below described bonding agent was applied to the cord, the cord was strengthened by hot bonding under a 12 percent stretch at 200 C. for 20 minutes. The measurement results for adhesion and resistance to fatigue were as given in Table l. The measurements of resistance to fatigue were made by the Goodyear Fatigue Test, 118 L 10174963.

Adhesion was tested by the Hobverse side pulling test. The bonding agent used during the bonding treatment had the following composition:

condensation product offormaldehyde and resolein styrene-butadiene copolymer styrene-butadlene-vinylpyridine (er-polymer As is clear from the results shown in the Table l, the treating agent containing components X and Y within the compositional limits covered by the present invention, as when used in Tests No. 1-6 produced the result of raising the strength, adhesion and fatigue resistance of the cord subsequent to hot bonding treatment. i

In contrast, there is an undesirable reduction in cord strength inTests 7 and 9 (when there is insufiicient component X) and in Test No. 8 when there is insufficient Y.

Further, in Tests 10 (when an excessive quantity of component X is used), Test 1 1 (when an excessive quantity of Y is used), and Test 12 (when there is an excessive quantity:of both the X and Y components,) the strength of the cord is increased; however, there is an undesirable drop in adhesion and fatigue resistance.

The results in Tests 13 (when only component Y is used) are also undesirable since the strength of the cord is not raised sufficiently and the fatigue resistance drops.

TABLE 1 [Method covered by the present invention] Test number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 blank Composition of the-processing agents InrlinlLv oxidized polyethylene Y:

(omponnd A (mnponnd 1i (oniponnd Nonionie. snrlnee (otnponnd F. Lubricating rurent:

Mineral oil, Redwood viscosity at- Compound D represented by the following formula:

30 (1., lit) th... 70. 0 40. 0 50. 0 70. 0 40. [l 70. 0 30. 0 67 0 30. 0 (10.0 30 150 See 72. 0 40. 0 40. 0 70 0 30. 0 Surface netive agent:

llluher alcohol ethylene oxide addition product 24. ii 19. 9 28. 0 22. 0 17. 0 17. O 26. I 19. 25. 0 23. 0 21 0 21 0 30 0 40. 0 30.0 Alkyl sulfate 10.0

( ord properties:

Untreated cord Strength, kg 15. 0 15. 0 15. 0 15. 0 15. 0 15. 0 15. l) 15. 0 15. 0 15. 0 15. 0 15. 0 15. 0 15. 0 15. 0 15. 0 Treated cord strength, kg 15. 1 16. 2 15. 6 15. 2 15. 6 15. 5 14. 5 14. 5 14. 6 15. 5 15. 3 15. 5 l4. 8 14. 0 14. 3 1-1. 0 Bonding Strength, kg 14 13 14 14 13 13 14 13 13 12 13 11 13 11 l4 11 Fatigue resistance, percent 150 130 130 110 120 120 120 80 80 80 80 100 10 0 Explanation of Table 1 70 CH20-C()(CH2)1o-CH-(CH2)5-CH3 In Cthe fotegtglltlg table, OomfioundsQA-F represented the ffllowifigg: I 0 (OH CH2 0) U 1 O r 5 nin 2 p fiiniiitii; 6; i d 6 1: 111-04: o(c1-n toCH-(CH2) 5-0113 ompoun 0 one astman ompany aci va ue softening point 105 0., specific gravity 0.94. 5 O (CH gfi ag Compound C=AC655 (Allied Chemical Company) acid value 15, 2 2 3 softening point104 0., specific gravity 0.03. 75 H Compound E Same formula D-i-q-H= 100 Compound F represented by the following formula:

CHz-OCO-(CH2)1CH=CHCH -OH(CHZ) CH In contrast, in the comparative examples (Tests No. 2 and 3) only the adhesion is raised. The strength of the treated cord is reduced and absolutely no increase in fatigue resistance can be observed, since the nonionic surface active agent used dif- 5 fered from that covered by the present invention, giving undesirable results.

Example 3 A treating agent with the composition shown below was applied to nylon tire cord-as the first paragraph of the exam The results in Test 14 (when only component X is used) are undesirable since strength, adhesion and fatigue resistance are all reduced.

Further, in Test 15 (when neither component X nor Y were used and only the mineral oil and the alkyl sulphonic acid salt were used), adhesion is raised, however, both strength and fatigue resistance drop.

A spinning oil with the composition listed above was applied in a quantity of 0.5 weight percent to nylon 6 tire cord during the spinning process producing improved spinnability. Subsequent to spinning and hot elongation, tire cord similar to that of Example 1 was produced. After treating this cord with the same bonding agent as shown in Example I, it was heat treated at 200 C for seconds and a stretch of l2 percent.

Example 2 The results of measuring the strength of the cord, adhesion A treating agent with the composition shown below was apand fatigue resistance as in Example 1, were as given in Table plied to nylon tire cord during the spinning process in a 10 3.

percent aqueous emulsion and in a quantity of 0.5 weight per- TABLE 3 cent to the fiber. After spinning and hot stretching, a 840 denier, 2 ends, 47 filaments per end, tire cord was formed. After C d t t db th treating this cord with the bonding agent as shown in Example f, fi inethe gs? No. 1, it was stretched l2 percent at 200 C. for 20 seconds present invention under heat. The results of measurements made of the strength, fatigue resistance and adhesion of the cord were as given in Strength of the unnamed Table 2. cord, Kg 15.0 15.0

As is evident from the above table, satisfactory results are strength of "sated derived in increasing the strength, the adhesion and the Adhesion, Kg 14.0 11.0 fatigue re. tance of the cord that is treated by the method F i resismmg 170 covered in the present invention.

TABLE 2 Comparative example Present Composition of the treatment agent invention Blank Partially oxidized polyethylene Y:

-655 (Allied Chemical Co. mfg.) acid value 15, softening point 1 2 3 4 104 C., percent. 2.0 Nonionic surface active agent:

Hz0 (JO-(CH2) 7CH=CHCHz-CH-(CH:)5CH;

30. 0 O(CHzCHzO) H CH2O C O(CHz)1CH=CHCHzCH(OHz)5GH3 O-(CHzCHzO),-H t +q+ Polyoxyethylene-(20)-castor oil ester, percent GHQ-(CH2) i1O(CHzC1-IzO)mII Polyoxyethylene-(20)-lauryl ether, percent 30. 0 CH3(CH2)io O O(CHzCH20)2o-H Polyoxyethylene-(QO)-lauryl ester, percent. 30. O Lubricating agent: Mineral oil (Redwood viscosity see.), percent 50 50 50 Ionic surface active agent:

Alkyl phosphoric acid ester, percent 15 15 15 Alkyl sulfonate, percent 3 3 3 Properties of the cord:

Untreated cord strength, kg 15. 0 15. 0 15. 2 15.0 Treated cord strength, kg. 15. 2 14. 6 14. 8 14. 0 Bonding strength, kg 14. 0 14. 0 14. 2 11 Fatigue resistance, percent 150 100 100 100 It was possible to obtain superior results in cord strength, adhesion and resistance to fatigue with the application of the present invention.

Example 4 A treating agent with the composition shown below was applied to nylon tire cord-as the first paragraph of the examples.

Petrolite PE-lOO, partially oxidized microcrystalline wax,

Petrolite lE-lOO, partially oxidized microcrystalline wax, acid value -20,

softening point 195 C Mineral oil Redvdvis's'ity'155035556 255': II. III III III: III III TABLE 4 Cord processed by Degreased the method covered cord in the present (blank invention test) Strength of the untreated cord, Kg 15.0 14.8 Strength of the treated cord, Kg 15.2 14.0 Adhesion, Kg 14.0 11.0 Resistance to fatigue, 140.0 100.0

The strength and the resistance to fatigue of the cord treated by the method covered in the present invention is increased dramatically over that of the untreated cord.

Example 5 A treating agent with the composition shown below was applied to nylon tire cord-as the first paragraph of the examples.

Vp-500l Hexto Company, oxidized polyethylene, acid value \gjOll Ilexto Company, oxidized polyethylene, acid value 12, softening point 1 where p+q+1-=40 Mineral oil (Redwood viscosity 150 sec. at C.)

the composition shown above to apply 0.7 weight percent to the cord. It was then bonded by stretching 0 percent at 230 C. for seconds. The results of measuring the strength of the cord after treatment were as given in Table 5.

The bonding agent used during the bonding treatment was the bonding compound shown in Example 1, to which 5 weight percent of Epicoat 812 was added. This compound was applied in an amount equal to 8 percent ofthe fiber.

Percent weight TABLE 5 Strength after bonding treatment 14.7 Kg 14.3 Kg

14.7 Kg 13.0 Kg

14.9 Kg 13.8 Kg

Example 6 A treating agent with the composition shown below was applied during the spinning of nylon tire cord. 10 percent aqueous emulsions in which the molar numbers (p q r) of ethylene oxide added to a polyoxyethylene castor oil ester were varied, were applied to the cord in amounts equivalent to 0.5 weight percent. The cord was hot stretched to form a 840 denier, 2 ends, 47 filaments per end, tire cord. After treating this cord with a bonding agent similar to that described in Example it was hot stretched 12 percent at 200 C. for 20 seconds. The results of measuring the strength, resistance to Percent weight fatigue and adhesions of the cord were as given in Table 6.

Composition of the treating agent. Polyoxyethylene castor oil ester.

Percent; (|3Hz-OC0-(C1191-CH CH-OHg-C1I(CHz) -CIl; O" (CIIZ CI'I2 O)i-II (III-O CO(CII2)7CII:CIICII2'CH'-'(CH2)5 CH3 O(CH2-CH20) qH CIIzO C-(ClIg)1CII=CHCH1-CH(CHz)5-CH3 O(CHzOHz-O),H 4. Glycerol di-glycidyl ether, I Epolene E, Eastman Company, partially oxidized polyethylene, acid value 12,

softening point 97 C 0.1 Mineral oil (Redwood viscosity 60 seconds) 0 Alkyl phosphoric acid ester 2o. 0

Com-

para- Cord produced by the method covered in Comparative tive the present invention example Molar number for the ethylene oxide added p-l-q-l-r 5 24 40 100 300 305 Blank Strength of the untreated cord. kg 15.1 15.1 15.1 15.0 15.0 15.0 15.0 15. 0 15.0 Strength of the (rented cord, kg. 15. 2 15.3 15. 2 15. 2 15, 2 15. 2 15. 0 14. 0 14. 0 Adhesion. kg 15.0 15.8 14.0 14.0 14.0 14.2 14.3 14.4 11.0 Fatigue resistance. percent 131 130 130 130 130 130 120 115 100 As is clear from the above table the strength, adhesion and fatigue strength of the treated cord with the molar numbers, p q r of the ethylene oxide added within the limits of 5 to 300 as in the method covered by the present invention were superior. Conversely, when the molar numbers of the ethylene oxide added were low (p q r= 4), the strength and fatigue resistance raised but adhesion was insufiicient.

Further, when the molar numbers of the ethylene oxide added were high (p q r 305) no treatment effects appeared owing to difficulty in emulsification, adhesion was improved. However, no improvement in strength was observed and there was little increase in fatigue resistance.

1 CLAIM:

l. A method for the treatment of synthetic fibers used for reinforcing rubber comprising applying a thin coating of a treating agent to said fibers, said treating agent comprising a. 5 to 40 percent by weight of the said treating agent of a nonionic surface active agent having the following general formula:

where A represents (CH ),-CH Cl-l-CH or (Cl-1 R R and R represent hydrogen atoms -CO-R ,-CO-R or -CO- R;,; and R',, R and R;, represent aliphatic hydrocarbons with carbon numbers of 1 to 22, p, q, and r represent the molar numbers of the ethylene oxide added and p q r is a positive integer= 5 to 300,

b. 0.1 to 3.0 percent by weight of the said treating agent of partially oxidized polyethylene with an average molecular weight of 500 to 10,000,

0. the remaining percent by weight of the said treating agent of a lubricating agent for said fibers and an ionic surface active agent or a nonionic surface active agent which is different from the nonionic surface active agent in (a).

2. The method of claim 1 wherein the synthetic fiber is selected from the group consisting of nylon and polyester, the coating is applied to achieve 0.01 to 2.0 percent by weight of the fiber, the partially oxidized polyethylene has an acid value of 10 to 30 and a softening point below C., the lubricating agent is a mineral oil, a higher aliphatic alcohol ester, or a vegetable oil, and the second surface active agent is a higher alcohol-ethylene oxide adduct, a sulfuric acid ester salt, or a phosphoric acid ester salt.

3. The method of claim 2 wherein the nylon is nylon 6, and R R and R have carbon numbers of 8 to 17.

4. The method of claim 2 wherein the polyester is polyethylene terephthalate, and R R and R have carbon numbers of8 to 17. 

2. The method of claim 1 wherein the synthetic fiber is selected from the group consisting of nylon and polyester, the coating is applied to achieve 0.01 to 2.0 percent by weight of the fiber, the partially oxidized polyethylene has an acid value of 10 to 30 and a softening point below 125* C., the lubricating agent is a mineral oil, a higher aliphatic alcohol ester, or a vegetable oil, and the second surface active agent is a higher alcohol-ethylene oxide adduct, a sulfuric acid ester salt, or a phosphoric acid ester salt.
 3. The method of claim 2 wherein the nylon is nylon 6, and R1'', R2'' and R3'' have carbon numbers of 8 to
 17. 4. The method of claim 2 wherein the polyester is polyethylene terephthalate, and R1'', R2'' and R3'' have carbon numbers of 8 to
 17. 